Back focus issue - lens test done - what's next?

[reader0428]

OK - I did the testing setup today (all shots on a tripod with self-timer to release the shutter). I tried my Canon 50mm/1.4, Canon 85mm/1.8, and Tamron 28-75/2.8. Surprisingly, the Tamron is just fine, but my two primes are having issues. :(

The 50mm does OK when I am focusing fairly close - had 2 shots that were fairly OOF at my focus point (at 1.8 and 2.2, but other than that it was not too bad. The pencil indicates where I set the focus point. (Color shifts are due to the sun going in and out from behind clouds.) Auto focus used on all with the center focus point selected. All photos have been cropped for easier viewing.

50mm, 1.8, close focus: (OOF)



50mm, 2.0, close focus: (not bad)



50mm, 2.2, close focus (OOF)



However, when I moved the camera farther away from the tape measure, that's when I really saw the problem. EVERY SHOT was off by quite a bit.

50mm, 2.0, farther focus


50 mm, 2.2, farther focus


50 mm, 2.8 farther focus (this aperture looked good with closer focus)


Same thing all the way up through the f/stops, of course the problem becomes less noticeable the more depth of field there is.

Then with the Tamron:

55mm, 3.2



75mm, 2.8


No problems with this lens.

So what's next? Can I take them to a local shop in Houston to get fixed? I'm not really excited about spending as much in repairs as what the lens is worth...but I can't keep going with these problems. I bought the 85mm new from Amazon and have all paperwork (but never sent in warranty card); the 50mm I bought used from this forum and have no box or paperwork.

[Fireball]

Wow, I hope you get it figured out cuz I tried back focusing for awhile and could never get used to it and went back to the shutter button instead. Wondering if it's worth it or just a matter of practice.

[reader0428]

Let me clarify - when I say "back focus", I'm referring to the fact that the lens is focusing behind the selected focus point instead of where it is supposed to focus - I'm not using the back focus button.